For each parameter not used: introduce "replace with repeat"

An enhancement for KT-27209

idea/src/org/jetbrains/kotlin/idea/inspections/ForEachParameterNotUsedInspection.kt

@@ -11,14 +11,20 @@ import com.intellij.codeInspection.ProblemHighlightType
 import com.intellij.codeInspection.ProblemsHolder
 import com.intellij.openapi.project.Project
 import com.intellij.psi.PsiElementVisitor
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.VariableDescriptor
 import org.jetbrains.kotlin.descriptors.impl.ValueParameterDescriptorImpl.WithDestructuringDeclaration
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
+import org.jetbrains.kotlin.idea.caches.resolve.resolveToCall
+import org.jetbrains.kotlin.idea.core.moveFunctionLiteralOutsideParentheses
+import org.jetbrains.kotlin.idea.core.replaced
 import org.jetbrains.kotlin.idea.intentions.SpecifyExplicitLambdaSignatureIntention
+import org.jetbrains.kotlin.idea.project.builtIns
 import org.jetbrains.kotlin.idea.refactoring.getThisLabelName
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.BindingContext
+import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
 import org.jetbrains.kotlin.resolve.calls.model.VariableAsFunctionResolvedCall
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameOrNull
@@ -45,11 +51,16 @@ class ForEachParameterNotUsedInspection : AbstractKotlinInspection() {
                     if (iterableParameter !is WithDestructuringDeclaration &&
                         !lambda.bodyExpression.usesDescriptor(iterableParameter, context)
                     ) {
+                        val fixes = mutableListOf<LocalQuickFix>()
+                        if (it.parent is KtDotQualifiedExpression) {
+                            fixes += ReplaceWithRepeatFix()
+                        }
+                        fixes += IntroduceAnonymousParameterFix()
                         holder.registerProblem(
                             calleeExpression,
                             "Loop parameter '${iterableParameter.getThisLabelName()}' is unused",
                             ProblemHighlightType.GENERIC_ERROR_OR_WARNING,
-                            IntroduceAnonymousParameterFix()
+                            *fixes.toTypedArray()
                         )
                     }
                 }
@@ -71,6 +82,28 @@ class ForEachParameterNotUsedInspection : AbstractKotlinInspection() {
         }
     }
 
+    private class ReplaceWithRepeatFix : LocalQuickFix {
+        override fun getFamilyName() = "Replace with 'repeat(size)'"
+
+        override fun applyFix(project: Project, descriptor: ProblemDescriptor) {
+            val callExpression = descriptor.psiElement.parent as? KtCallExpression ?: return
+            val qualifiedExpression = callExpression.parent as? KtDotQualifiedExpression ?: return
+            val receiverExpression = qualifiedExpression.receiverExpression
+            val receiverClass =
+                receiverExpression.resolveToCall()?.resultingDescriptor?.returnType?.constructor?.declarationDescriptor as? ClassDescriptor
+            val collection = callExpression.builtIns.collection
+            val sizeText = when {
+                receiverClass != null && DescriptorUtils.isSubclass(receiverClass, collection) -> "size"
+                else -> "count()"
+            }
+            val lambdaExpression = callExpression.lambdaArguments.singleOrNull()?.getArgumentExpression() ?: return
+            val replacement =
+                KtPsiFactory(project).createExpressionByPattern("repeat($0.$sizeText, $1)", receiverExpression, lambdaExpression)
+            val result = qualifiedExpression.replaced(replacement) as KtCallExpression
+            result.moveFunctionLiteralOutsideParentheses()
+        }
+    }
+
     private fun KtBlockExpression?.usesDescriptor(descriptor: VariableDescriptor, context: BindingContext): Boolean {
         if (this == null) return false
         var used = false

idea/testData/inspectionsLocal/forEachParameterNotUsed/normal.kt

@@ -1,4 +1,5 @@
 // WITH_RUNTIME
+// FIX: Introduce anonymous parameter
 
 fun test(list: List<String>) {
     list.for<caret>Each {}

idea/testData/inspectionsLocal/forEachParameterNotUsed/normal.kt.after

@@ -1,4 +1,5 @@
 // WITH_RUNTIME
+// FIX: Introduce anonymous parameter
 
 fun test(list: List<String>) {
     list.forEach { _ -> }

idea/testData/inspectionsLocal/forEachParameterNotUsed/repeat.kt

@@ -0,0 +1,6 @@
+// WITH_RUNTIME
+// FIX: Replace with 'repeat(size)'
+
+fun test(list: List<String>) {
+    list.for<caret>Each {}
+}

idea/testData/inspectionsLocal/forEachParameterNotUsed/repeat.kt.after

@@ -0,0 +1,6 @@
+// WITH_RUNTIME
+// FIX: Replace with 'repeat(size)'
+
+fun test(list: List<String>) {
+    repeat(list.size) {}
+}

idea/testData/inspectionsLocal/forEachParameterNotUsed/safe.kt

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun test(list: List<String>?) {
+    list?.for<caret>Each {}
+}

idea/testData/inspectionsLocal/forEachParameterNotUsed/safe.kt.after

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun test(list: List<String>?) {
+    list?.forEach { _ -> }
+}

idea/testData/inspectionsLocal/forEachParameterNotUsed/sequence.kt

@@ -0,0 +1,6 @@
+// WITH_RUNTIME
+// FIX: Replace with 'repeat(size)'
+
+fun test(sequence: Sequence<String>) {
+    sequence.for<caret>Each {}
+}

idea/testData/inspectionsLocal/forEachParameterNotUsed/sequence.kt.after

@@ -0,0 +1,6 @@
+// WITH_RUNTIME
+// FIX: Replace with 'repeat(size)'
+
+fun test(sequence: Sequence<String>) {
+    repeat(sequence.count()) {}
+}

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -2542,6 +2542,21 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
         public void testNormal() throws Exception {
             runTest("idea/testData/inspectionsLocal/forEachParameterNotUsed/normal.kt");
         }
+
+        @TestMetadata("repeat.kt")
+        public void testRepeat() throws Exception {
+            runTest("idea/testData/inspectionsLocal/forEachParameterNotUsed/repeat.kt");
+        }
+
+        @TestMetadata("safe.kt")
+        public void testSafe() throws Exception {
+            runTest("idea/testData/inspectionsLocal/forEachParameterNotUsed/safe.kt");
+        }
+
+        @TestMetadata("sequence.kt")
+        public void testSequence() throws Exception {
+            runTest("idea/testData/inspectionsLocal/forEachParameterNotUsed/sequence.kt");
+        }
     }
 
     @TestMetadata("idea/testData/inspectionsLocal/ImplicitNullableNothingType")